According to IGN, under climate warming, tree mortality has more than doubled over twenty years in metropolitan France.
Climate Change to Blame
It’s a sad paradox: on one hand, France’s forests keep expanding. On the other, they are increasingly in poor health. In mainland France, forests cover about 17.7 million hectares, roughly one-third of the land. An area that has risen by an average of 100,000 hectares per year over the past 15 years (about 247,000 acres annually). But most species are affected by this growing mortality, “some because of specific diseases and others probably more by the recurrence of droughts and heatwaves or other climatic hazards”, notes IGN, the French National Institute for Geographic and Forest Information.
The assessment it outlines for the period 2016-2024, i.e., before the recent wave of fires and the historic drought of last summer, is dramatic: over the last two decades, tree mortality has been multiplied by 2.5. The annual mortality of our forests averages 18.1 million cubic meters (Mm³/year) over 2016-2024, compared with 7.4 Mm³/year over 2005-2013.
Less Carbon Sequestration
According to IGN, this rise “highlights the burden environmental changes and biotic threats place on forests.” Fungi, insects, and bacteria are thriving. With climate warming, trees are becoming increasingly vulnerable. Climate conditions can also be favorable to certain wood-boring insects, notably bark beetles. This poor health calls into question the ability of France’s forests to sequester carbon. According to IGN, the French forest sink has absorbed an average of 39 million tonnes of CO2 per year during 2016-2024, down from 63 million tonnes per year in 2005-2013. A slowdown of about 38%.
In the end, most species are affected by this increasing mortality. “Some due to specific diseases and others probably more by the recurrence of droughts and heatwaves or other climatic hazards.” Result: the average annual biological production, i.e., the growth of all trees, is “significantly down” by about 8% over the last ten years, still compared with the 2005-2013 period.
